Wind energy facility with a closed cooling circuit

ABSTRACT

The conversion of energy regularly results in losses in the form of heat. This applies both for the conversion of kinetic energy of wind into electrical energy in the generator of a wind energy facility, where these losses regularly occur in the main driving line of the wind energy facility, and also for the electrical feeding of energy generated by the wind energy facility into a medium voltage network. For this purpose, regular devices of power electronics, e.g., rectifiers, and/or transformers, are necessary. In the main driving line, which is mounted in the nacelle for a wind energy facility, the losses occur overwhelmingly in the gears, at the bearings, and in the generator or at other control units, such as, e.g., in the hydraulic systems or similar control and regulation units, which adjust the rotor blades or turn the wind energy facility into the wind. For gearless wind energy facilities, e.g., model E-66 of Enercon, the main losses occur at the main driving line in the generator, i.e., in the nacelle (head) of the wind energy facility. The task of the invention is to prevent the previously mentioned disadvantages and to provide a cooling device for a wind energy facility, which reduces the losses of the wind energy facility. Wind energy facility with a completely closed or at least partially closed cooling circuit, with which the heat to be dissipated from the cooling circuit is dissipated by the tower or the nacelle of the wind energy facility.

BACKGROUND OF THE INVENTION

The conversion of energy regularly results in energy being lost in theform of heat. This applies to both the conversion of thee kinetic energyof wind into electrical energy in the generator of a wind energyfacility, where these losses regularly occur in the main driving line ofthe wind energy facility, and also for the electrical feeding of energygenerated by the wind energy facility into a medium voltage network. Forthis purpose, regular devices of power electronics, e.g., rectifiers,and/or transformers, are necessary. In the main driving line, which ismounted in the nacelle for a wind energy facility, the losses occuroverwhelmingly in the gears, at the bearings, and in the generator or atother control units, such as, e.g., in the hydraulic systems or similarcontrol and regulation units, which adjust the rotor blades or turn thewind energy facility into the wind. For gearless wind energy facilities,e.g., model E-66 of Enercon, the main losses occur at the main drivingline in the generator, i.e., in the nacelle (head) of the wind energyfacility.

For the power supply, losses occur overwhelmingly at the powertransformer and, if necessary, in the power electronics, e.g., in therectifier.

For a 1.5 MW wind energy facility, the losses can be in the range of60-100 kW. Up until now, these losses ere dissipated into theenvironment by means of fans. In this way, cold air is suctioned in fromthe outside by the fans to cool the corresponding components, e.g., thegenerator. The heated air is then blown back outside.

Consideration has also already been given to cooling the generator withwater and to then cooling the heated water back down with a heatexchanger. All of these known solutions have in common a large amount ofair that is always needed from the outside. This is particularlydisadvantageous if the outside air is humid or, particularly in coastalregions, if it has a high salt content, and the cooling elements arethen exposed to this humid and high salt content air. This problem isespecially extreme with wind energy facilities that stand directly onthe coast or, in offshore technology, directly in salt water.

SUMMARY OF THE INVENTION

One object of the invention is to provide a cooling device for a windenergy facility which reduces its losses.

The basic concept of the invention is to provide a completely closed orin an alternative embodiment, a partially closed cooling circuit for awind energy facility, so that no or practically no outside air has to beused for cooling. In this way, the cooling air circulates within thewind energy facility from its nacelle to the tower or to the base of thewind energy facility and the energy stored by the coolant, preferablyair, during the cooling is dissipated by means of the tower of the windenergy facility. The tower of the wind energy facility is always exposedto the wind, so that the tower of the wind energy facility acts as acooling element or a heat exchanger, which dissipates the stored energyto the wind enveloping the tower.

Another advantage of the concept according to the invention is that thetower is also heated from the inside out for very cold outsidetemperatures of approximately −20° to −30° C. by its function as a heatexchanger and a load-bearing part of the wind energy facility. Due tothis fact, the wind energy facility can remain in operation. Accordingto the state of the art up until now, a special cold-resistant steel hadto be used for very cold locations, such as, e.g., northern Sweden,Norway, Finland, Canada, etc.

If desired, due to very low outside temperatures below the freezingpoint, it is also possible to combine the heating of the rotor bladeswith the cooling circuit, so that the rotor blades can be heated withthe fluid in the cooling circuit.

The coolant is cooled by the tower due to the fact that at least one airchannel is formed in the tower itself (inside or outside), and theheated air flows through this channel such that the air can dissipateits energy at least partially at the tower walls.

One air channel is preferably formed such that the tower is configuredwith double walls, so that one part of the cooling channel is formedthrough the load-bearing wall of the tower.

By using the tower or rotor blades of the wind energy facility, whichare usually manufactured out of steel, as a cooling element or a heatexchanger, a component that is already present and required by everywind energy facility is used for an advantageous function. Heated airflows from the generator or transformer into the steel tower at itsouter wall. This outer wall has a very large surface area, e.g., for a1.5 MW facility, approximately 500 m², and thus offers a very largeheating/cooling surface. The wind enveloping the tower continuouslycools this surface.

When the blades are used a the heat exchanger, this provides rapidcooling since they present a large surface area that rotates through thewind at high speeds. The further advantage is that the rotor blades areheated, which is an advantage in ice forming conditions since it willkeep the blades free of snow and ice and save the expense of providing aseparate heater for the rotor blades.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 shows the correlation between cooling power and wind speed.

FIG. 2 shows the correlation between generator power and wind speed.

FIG. 3 shows an embodiment of the invention with reference to a windenergy facility.

FIG. 4 shows a cross section of the tower walls cut along the line A—Afrom FIG. 3.

FIG. 5 shows an alternative embodiment of the cooling circuit accordingto FIG. 3.

FIG. 6 shows an additional embodiment of a wind energy facilityaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The possible cooling power of the wind increases with rising wind speed.This correlation is shown in FIG. 1. With rising wind speed, thegenerator power also rises, and thus, also the heat created by thegenerator due to power loss. The correlation between the generator powerand the wind speed is shown in FIG. 2. Thus, rising heat due toincreased power losses can be dissipated relatively easily because thecooling power of the tower of the wind energy facility also rises withthe increasing power loss.

FIG. 3 shows an embodiment of the invention with reference to a windenergy facility according to model E-66 from Enercon, which provides agenerator power of 1.5 MW. FIG. 3 shows a cross section of a wind energyfacility 1 in with a nacelle 2 at the end of the head, which issupported by a tower 3. This tower 3 is anchored in the ground (notshown).

The nacelle 2 houses the main driving line of the wind energy facility.This main driving line comprises a rotor 4 with rotor blades 5 (only thebase of which are shown for ease in illustration), as well as agenerator 40 connected to the rotor. This generator 40 has a generatorrotor 6 and a generator stator 7. If the rotor 4, and thus the generatorrotor 6, turns, then electrical energy, e.g., as alternating current (oras direct current) is generated.

The wind energy facility further has a transformer 8, and in someembodiments a rectifier 9 connected in series before this transformer 8.The rectifier 9 supplies electrical energy in the form of alternating orthree-phase current to the transformer 8. The transformer 8 feeds theenergy generated by the wind energy facility into a network, preferablya medium voltage network (not shown).

The tower 3 is configured in sections with double walls 13 and 14, ascan be seen in FIG. 3, and in each double-walled region, a coolingchannel is present. In this cooling channel 11, a fan 10 is provided(several fans can also be provided), which drives the air through thecooling channels 11. A return channel 12 is also provided.

In one alternative embodiment, a cooling channel 11 a runs also throughthe blades 5, as shown in FIG. 3. This cooling channel 11 a has a dualfunction, to cool the generator and also to heat the rotor blades. Inthose environments where snow or ice build up on rotor blades and mayprevent efficient operation, use of the already present and locallygenerated heat to provide the deicing is much more economical sinceheaters may not need to be installed for deicing on the rotor blades.Also, the rotor blades provide a broad, exposed surface area for raidcooling and dissipation of large amounts of heat. The cooling channels11 a are preferably located on those edges most susceptible to ice buildup, so that a direct heat transfer from the fluid to the part of theblade needing the heat occurs. Alternatively, one or more coolingchannels 11 a can be located on the broad front exposed surface of theblade for the most exposure to the large surface area in the wind.

The cooling fluid used is any accepted coolant. In a preferredembodiment, the cooling fluid is air. The air is preferably dry air thathas been placed in the channels from ambient air on days of low moisturein the ambient air. Of course, the air can be made more dry bydehumidifiers if desired. Using dry or conditioned air with moistureremoved will ensure that even on very cold days, no moisture from theair condenses out and freezes inside the channels 11, 12 or 11 a. Ifparticularly clean, moisture free air is desired, it can be filtered toremove all water vapor or pure nitrogen gas or other heat transfer gascan be used. A liquid, such as antifreeze can be used for the coolingfluid if desired.

FIG. 4 shows a cross section of the tower walls cut along the line A—Afrom FIG. 3. It can be seen here that in the illustrated example, twocooling channels 11, 12 are formed, and the tower is configured in acertain region with double walls. The air heated by the generator nowflows through an air channel out of the machines in the nacelle 2 intothe upper tower region. There, the heated air is directed to the innerside of the steel tower. As already mentioned, the steel tower isconfigured with double walls over a great length, e.g., approximately50-80%, with an outer wall 13 and an inner wall 14, and there it formsthe cooling channel 11. Here, the inner wall 14 in the cooling channelcan be made of a simple material, e.g., plastic or cloth. The heated airfrom generator 40 must now flow along a large stretch on the inside ofthe steel tower 3. In this way, the tower or its steel is heated over alarge surface area and the air is cooled.

In the lower region of the lower there is the rectifier 9 and the mediumvoltage transformer 8 (and/or additional electrical devices). Thesecomponents must also be cooled. The cooled generator air is now guidedfirst through the rectifier 9. Here, the devices of the powerelectronics are actively cooled. The air output from the rectifier isnow further guided to the transformer 8 and also cools the transformer.Subsequently, the air rises through the second cooling channel 12 backupwards to the machine house and to the generator 40.

The cooling circuit is thus closed and it is not necessary to introducecooled air from the outside.

For cooling all components, particularly sensitive components, the windenergy facility always uses the same air. It is a closed system, andonce sealed with the proper air, is not later opened.

If necessary, air filters and additional cooling devices (e.g., heatexchangers) can obviously also be mounted in the cooling channel, ifdesired.

The advantages of the invention consist in the fact that no high saltcontent or humid air comes into contact with the sensitive components,such as generators, rectifiers, and transformers. The risk of corrosionis thus drastically reduced within the machine housing and the tower. Inthe wind energy facility, particularly in its tower, there can be nobuild up of mold or fungi.

In one alternative embodiment, the cooling channel may have a valve thatcan be held open at all times or selectively opened. If it is desired toexchange outside air with the cooling fluid, the valves can be opened sothat some or all of the cooling fluid is obtained from ambient air andis exhausted to ambient air. In some dry environments that require extracooling, this may be preferred, such as in large desert areas from theocean, such as Saudi Arabia, Arizona, New Mexico, and the like. Thesystem can thus be a partially closed system in one alternativeembodiment or a system that can be selectively opened and closed in yeta further embodiment.

In total, for the cooling of the entire wind energy facility,considerably less energy is required than before because (secondary)cooling power is produced from the outside of the tower by the wind.

By forming cooling channels in the rotor blades and by connecting thesecooling channels to the cooling circuit according to the invention, itis also possible to introduce the air heated by the generator first intothe cooling channels of the rotor blades, so that during cold periods,particularly for temperatures around the freezing point, the rotorblades can be deiced. The formation of cooling channels in a rotor bladeis also known, e.g., from DE 195 28 862.9.

The formation of the cooling channels in the machine housing is donethrough corresponding walls and air guiding devices, which direct theair such that it passes the elements, such as, e.g., the generator.

If the cooling power of the tower is not sufficient, e.g., on very warmdays, it is also possible to use additional cooling elements, such as,e.g., conventional heat exchangers, in the cooling circuit.

FIG. 5 shows an alternative embodiment of the cooling circuit accordingto FIG. 3. Here, it can be seen that the wind energy facility has twoseparate and independent closed cooling circuits 15, 16, which eachdissipate stored heat to the tower. However, the two cooling circuits15, 16 are separated from each other, which is different than theconfiguration shown in FIG. 3. Here, each of the individual coolingcircuits 15, 16 has a passage or a cross channel within the tower 3 atthe turning point, so that the air flowing along one wall of the toweris directed to the opposite side of the tower and thus is further cooledfor the unit to be cooled, which can be the generator 40 or the powerelectronics of the transformer 8, rectifier 9 and other electronics. Thefluids in each circuit can be different from each other. The fluid intop circuit 16 can be air, while fluid in the bottom circuit 15 can beoil, for example.

FIG. 6 shows an additional embodiment of a wind energy facilityaccording to the invention. Here, an air channel, e.g., an exhaust tube17, leads through the interior of the lower tower section. It can extendalong only part or nearly all the length of tower 3. This can also beretrofitted very easily, e.g., to an existing wind energy facility andmounted or suspended in the tower 3. Heated air originating from a powerbox 18, e.g., 600 kW power box having a transformer and rectifiertherein, is guided upwards from the tower base through this exhaust tube17 and is output from the exhaust tube 17 into the tower. From there,the heated air flows back downwards after cooling at the tower walls andthere it can be suctioned again by a ventilation device 20 (for supplyair), which is coupled by means of an air hood 19 to the power box 18.The exhaust tube 17 can be connected directly at the air outlet of thepower box 18 or there can be a second ventilation device 21, whichsuctions the heated air of the power box 18 and blows it into theexhaust tube 17, at the input of the exhaust tube 17. The exhaust tubeis preferably made out of plastic and thus it is very easily realizedand has a very small weight, which simplifies its attachment andretrofitting to a wind energy facility. In one embodiment, the tower 3of FIG. 6 is a hollow tube that is generally closed and may be sealed.The exhaust tube 12 is placed, with the ventilation device 20 into theinterior of the tube. Air is circulated through the interior of thetower to provide cooling of the power box 18 and/or nacelle 2 having agenerator therein. The exhaust tube 17 and ventilation device 20 canalso be placed at the base of the nacelle and blow air downward into thetower 3. In this embodiment, the same air is repeatedly circulated tocool the various components and at the same time provide some heating ofthe tower as the heat is transferred. This is a closed system, or couldbe termed a partially closed system.

In an alternative embodiment, the tower 3 has no interior chamber but israther in the form of steel beams, such as I beam, twin I beams, or thelike. In this embodiment the exhaust tube 17 is placed along side themetal structure so that air exiting enters the open air adjacent thestructure and is cooled by the ambient air and steel tower. New ambientair enters the intake of the ventilation device 20. Such a system couldalso be retrofit to the generator 40 in the nacelle 2 if desired. Thesystem of FIG. 6 can be thus a partially closed system in which outsideair is obtained, placed in a closed system and circulated in a closedsystem for distance before it is released to open air.

For improving the cooling effect of the nacelle 2, the nacelle can becompletely or partially made out of metal, preferably aluminum, in orderto also take advantage of the cooling effect of the nacelle, which isconstantly enveloped by wind, and thus to increase the generatorcooling. Here, it can also be advantageous to equip the nacelle on theinside with a surface area increasing structure, e.g., cooling ribs.

As first tests show, the configuration of a closed cooling circuit withthe use of the air channel shown in FIG. 6 is extremely effective andparticularly cost effective, because the investment necessary fordeveloping an air channel, particularly a plastic exhaust tube, is onlyvery small in comparison with a heat exchanger and its constantmaintenance costs. In addition, the cooling is extremely effective.

I claim:
 1. Wind energy facility (1) with a completely closed or atleast partially closed cooling circuit, with which the heat to bedissipated from the cooling circuit is dissipated by the tower (3) orthe nacelle (2) of the wind energy facility (1).
 2. Wind energy facilityaccording to claim 1, characterized in that the tower (3) has at leastone cooling channel (11, 12), and the coolant, preferably air, flowsthrough this channel.
 3. Wind energy facility according to one of thepreceding claims, characterized in that both the driving line (3, 4) ofthe wind energy facility or parts of the driving line and/or theelectrical devices (8, 9) for converting the electrical energy areconnected to the cooling circuit.
 4. Wind energy facility according toone of the preceding claims, characterized in that the tower (3) isconfigured with two walls over at least two sections along itslongitudinal axis (FIG. 4) and a double-walled region forms a coolingchannel (12, 11), with which the heated air introduced into the coolingchannel dissipates its heat to the outer wall of the tower (3).
 5. Windenergy facility according to one of the preceding claims, characterizedin that the same air is used essentially continuously for cooling themain driving line (3, 4), as well as the devices (8, 9) of the powerelectronics.
 6. Wind energy facility according to one of the precedingclaims, characterized in that the cooling channel is supplied by atleast one fan (10) that serves to circulate air within the coolingcircuit.
 7. Wind energy facility according to one of the precedingclaims, characterized in that the wind energy facility can be kept inoperation even for outside temperatures of approximately −20° C. to −40°C., and the tower can be heated by the cooling circuit.
 8. Use of thetower of a wind energy facility as a cooling element and/or a heatexchanger for cooling air heated by devices that generate heat, e.g.,the driving line and/or electrical device for converting electricalenergy, of the wind energy facility.
 9. Wind energy facility accordingto one of the preceding claims, characterized in that the wind energyfacility has at least two completely closed or at least partially closedcooling circuits, wherein one cooling circuit serves for cooling thedriving line of the wind energy facility, and the other cooling circuitserves for cooling the electrical device for conversion of electricalenergy.
 10. Wind energy facility according to one of the precedingclaims, characterized in that there is at least one air line that servesto transport heated air.
 11. Wind energy facility according to claim 10,characterized in that the air line is formed by a tube connected to aheat generator, e.g., to the air outlet opening of an electrical devicefor converting electrical energy, and/or parts of the driving line(generator).
 12. Wind energy facility according to claim 11,characterized in that the tube is connected at the air inlet side to aventilation device (fan), by means of which heated air is blown into thetube.
 13. Wind energy facility according to one of the preceding claims10-12, characterized in that the tube is more than ten meters long,preferably more than twenty-five meters long, and it is formed in thelower part of the tower such that heated air originating from anelectrical device for converting electrical energy, e.g., at a switchingbox or a power box, is blown through the tube, and heated air is outputagain at the tube outlet, so that it can be cooled at the tower wall andthen flow back to the tower base.
 14. Wind energy facility according toone of the preceding claims, characterized in that the nacelle iscompletely or partially made out of a metal, preferably aluminum. 15.Wind energy facility according to claim 14, characterized in that thenacelle is equipped completely or partially with cooling ribs or othermeans for increasing the surface area of the nacelle.
 16. The windenergy facility according to claim 1, wherein the nacelle is equippedcompletely or partially with cooling ribs or other means for increasingthe surface area of the nacelle.
 17. The wind energy apparatus of claim16, wherein the cooling system is retrofit to the tower and includes afluid transport tube that is adjacent the tower walls.
 18. A wind energyapparatus comprising: driving line for converting kinetic energy of thewind into electrical energy, said driving line including a rotor, rotorblades, and a generator connected to said rotor; a nacelle for housingsaid driving line; a transformer connected to the electrical output ofthe generator for feeding said electrical energy into a voltage network;a tower for supporting said nacelle; and a cooling system located withinthe tower.
 19. The wind energy apparatus of claim 18, wherein the saidcooling system comprises: a tower cooling channel within said tower; anacelle cooling channel; a flow guiding device in said nacelle coolingchannel for directing fluid near said driving line; and a fluid flowingthrough said tower cooling channels and nacelle cooling channels forproviding heat exchange to outer walls of said tower.
 20. The windenergy apparatus of claim 19, wherein the cooling system furthercomprises: a cooling channel formed within said rotor blades, whereinsaid fluid, as heated by said generator, can circulate through saidrotor blade to heat said rotor blade.
 21. The wind energy apparatus ofclaim 19, wherein the inner walls of said tower cooling channel arccomprised of plastic.
 22. The wind energy apparatus of claim 19, whereinsaid cooling system further comprises: heat exchange devices mounted tosaid tower cooling channels for additional heat exchange.
 23. The windenergy apparatus of claim 18, wherein the said cooling system comprisesof: said tower configured in sections with double walls for forming twotower cooling channels; at least one nacelle cooling channel; at leastone flow guiding device in said nacelle cooling channel for directingfluid near said driving line; a first individual cooling circuit ispositioned at the lower portion of said tower, and fluid flows throughsaid tower cooling channels providing heat exchange to said rectifier,said transformer and outer walls of said tower; and a second individualcooling circuit is positioned at the upper portion of said tower,wherein fluid flows through said tower cooling channels and said nacellecooling channel providing heat exchange to outer walls of said tower,said generator, and said nacelle.
 24. The wind energy apparatus of claim23, wherein said cooling system further comprises: a cooling channelformed within said rotor blades, wherein fluid in said second individualcooling circuit is heated by said generator, and circulates through saidrotor blade to heat said rotor blade.
 25. The wind energy apparatus ofclaim 23, wherein the inner walls of said tower cooling channels arecomprised of plastic.
 26. The wind energy apparatus of claim 23, whereinsaid cooling system further comprises heat exchange devices mounted tosaid tower cooling channels for additional heat exchange.
 27. A heattransfer system comprising: a tower; a heat source adjacent said tower;an exhaust tube adjacent an interior section of said tower; and aventilation device coupled to said heat source for obtaining fluid andcirculating the fluid adjacent the tower.
 28. The heat transfer systemof claim 27, wherein said exhaust tube is connected to the outlet of apower box as the heat source for suctioning heated fluid from said powerbox and blowing it into said exhaust tube thereby cooling the power boxand heating the outer walls of said tower.
 29. The heat transfer systemof claim 28, further comprising a second ventilation device forsuctioning heated fluid from said power box and blowing it into theinput base of said exhaust tube thereby heating the outer walls of saidtower.
 30. The heat transfer system of claim 27, wherein the exhausttube is made of plastic.
 31. The heat transfer system of claim 27,wherein said tower is in the form of a hollow tube and the exhaust tubeis within the hollow tube of the tower for circulating fluid therein.32. The heat transfer system of claim 27, wherein said tower is a solidbeam tower and the exhaust tube is placed adjacent said tower.
 33. Theheat transfer system of claim 27, wherein the heat source is a windpowered generator located at a top position of said tower and saidexhaust tube extends from a top portion of said tower downward.
 34. Amethod for supplying heat exchange to a wind energy apparatuscomprising: cooling a generator by flowing fluid through a nacellecooling channel and near said generator; and transferring heat from saidfluid to an outer wall of a tower as said fluid flows downward through atower cooling channel.
 35. The method of claim 34, wherein said fluidalso flows through a rotor blade cooling channel within a rotor bladeupon completing flow near said generator in said nacelle coolingchannel, thereby heating said rotor blades.
 36. A method for supplyingheat exchange to a wind energy apparatus comprising: cooling a generatorby flowing a first fluid near said generator within a nacelle coolingchannel; heating an outer wall of a tower as the first fluid flowsthrough a first tower cooling channel; crossing through the middle ofsaid tower; circulating the first fluid within a first individualcooling circuit through said nacelle cooling channel, near saidgenerator, and through said first tower cooling channel; cooling atransformer by flowing a second fluid near said transformer within asecond tower cooling channel; heating an outer wall of said tower as thesecond fluid flows through said second tower cooling channel; andcirculating the second fluid within said second individual coolingcircuit.
 37. A method for supplying heat exchange to a wind energyapparatus comprising: positioning an exhaust tube in the middle of atower; blowing heated fluid from a power box positioned at base of saidtower into bottom end of said exhaust tube; heating outside walls ofsaid tower with said fluid exiting top end of said exhaust tube; andre-circulating said fluid back into said power box with said ventilationdevice.